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How to Identify the Green Horned Butt Caterpillar

Updated July 20, 2017

The tomato hornworm (Manduca quinguemaculata) referred to as the green horned butt caterpillar by gardeners, can reach a length of five inches. The worm or caterpillar can consume a large tomato plant in two days. The worm attaches to the underside of plants in the nightshade family, such as tobacco, eggplants, peppers, potatoes and tomatoes. The worm prefers the tomato plant and will infest it when there is a choice.

Locate a specimen for identification at dusk or dawn, as the worm dislikes heat and direct sunlight. The green colour of the worm makes it difficult to see. Look for stems missing leaves or leaf wilt. Dark green or black pellet droppings called frass will be on the lower leafs. You will be able to locate the worm in this area.

Lift the specimen from the plant with a pocket knife and place it in the jar. Find a well-lighted area and remove the worm from the jar and place it on the paper plate. The specimen can be anywhere from a half inch to 5 inches long. If the worm is small, you will need the magnifying glass to identify its characteristics. Larger worms will be easier to identify.

Look for a green colouring that allows the worm to blend in with the leaves of plants. The horn on the tail will be blue, dark green or black. The worm will have eight V-shaped white or yellowish strips across its torso. You may see white cocoons attached to the worm's body; they are not the worm's eggs. The small white cocoons are the pupae of the Braconid Wasp. The wasp is a parasitic insect that preys on the worm. They are nature's way of controlling the worm.

Tip

A safe way to eliminate the worm is to hand pick it from the plant and put it in soapy water. If it has Braconid Wasp pupae attached to it, let them do the job for you.

Things You'll Need

  • Pocket knife
  • Glass jar
  • Paper plate
  • Magnifying glass
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About the Author

Based in southern Indiana, Lee Tarrence has been writing since 1980. She was editor of the "Sky Valley News and Review" for seven years. Her articles have appeared in newspapers and regional magazines including the "Journal-America." Tarrence holds a Bachelor of Arts in journalism from Indiana University.